org.apache.log4j.net

Class SocketAppender

java.lang.Object

org.apache.log4j.AppenderSkeleton

org.apache.log4j.net.SocketAppender

All Implemented Interfaces:

Appender, OptionHandler

public class SocketAppender
extends AppenderSkeleton

Sends LoggingEvent objects to a remote a log server, usually a SocketNode.

The SocketAppender has the following properties:

• If sent to a SocketNode, remote logging is non-intrusive as far as the log event is concerned. In other words, the event will be logged with the same time stamp, NDC, location info as if it were logged locally by the client.

• SocketAppenders do not use a layout. They ship a serialized LoggingEvent object to the server side.

• Remote logging uses the TCP protocol. Consequently, if the server is reachable, then log events will eventually arrive at the server.

• If the remote server is down, the logging requests are simply dropped. However, if and when the server comes back up, then event transmission is resumed transparently. This transparent reconneciton is performed by a connector thread which periodically attempts to connect to the server.

• Logging events are automatically buffered by the native TCP implementation. This means that if the link to server is slow but still faster than the rate of (log) event production by the client, the client will not be affected by the slow network connection. However, if the network connection is slower then the rate of event production, then the client can only progress at the network rate. In particular, if the network link to the the server is down, the client will be blocked.

  On the other hand, if the network link is up, but the server is down, the client will not be blocked when making log requests but the log events will be lost due to server unavailability.

• Even if a SocketAppender is no longer attached to any category, it will not be garbage collected in the presence of a connector thread. A connector thread exists only if the connection to the server is down. To avoid this garbage collection problem, you should close() the the SocketAppender explicitly. See also next item.

  Long lived applications which create/destroy many SocketAppender instances should be aware of this garbage collection problem. Most other applications can safely ignore it.

• If the JVM hosting the SocketAppender exits before the SocketAppender is closed either explicitly or subsequent to garbage collection, then there might be untransmitted data in the pipe which might be lost. This is a common problem on Windows based systems.

  To avoid lost data, it is usually sufficient to close() the SocketAppender either explicitly or by calling the LogManager.shutdown() method before exiting the application.

Since:

0.8.4

Author:

Ceki Gülcü

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_PORT The default port number of remote logging server (4560).
static String	ZONE The MulticastDNS zone advertised by a SocketAppender

Fields inherited from class org.apache.log4j.AppenderSkeleton

closed, errorHandler, headFilter, layout, name, tailFilter, threshold

Constructor Summary

Constructors

Constructor and Description
SocketAppender()
SocketAppender(InetAddress address, int port) Connects to remote server at address and port.
SocketAppender(String host, int port) Connects to remote server at host and port.

Method Summary

Methods

Modifier and Type	Method and Description
void	activateOptions() Connect to the specified RemoteHost and Port.
void	append(LoggingEvent event) Subclasses of AppenderSkeleton should implement this method to perform actual logging.
void	cleanUp() Drop the connection to the remote host and release the underlying connector thread if it has been created
void	close() Close this appender.
String	getApplication() Returns value of the Application option.
boolean	getLocationInfo() Returns value of the LocationInfo option.
int	getPort() Returns value of the Port option.
int	getReconnectionDelay() Returns value of the ReconnectionDelay option.
String	getRemoteHost() Returns value of the RemoteHost option.
boolean	isAdvertiseViaMulticastDNS()
boolean	requiresLayout() The SocketAppender does not use a layout.
void	setAdvertiseViaMulticastDNS(boolean advertiseViaMulticastDNS)
void	setApplication(String lapp) The App option takes a string value which should be the name of the application getting logged.
void	setLocationInfo(boolean locationInfo) The LocationInfo option takes a boolean value.
void	setPort(int port) The Port option takes a positive integer representing the port where the server is waiting for connections.
void	setReconnectionDelay(int delay) The ReconnectionDelay option takes a positive integer representing the number of milliseconds to wait between each failed connection attempt to the server.
void	setRemoteHost(String host) The RemoteHost option takes a string value which should be the host name of the server where a SocketNode is running.

Methods inherited from class org.apache.log4j.AppenderSkeleton

addFilter, clearFilters, doAppend, finalize, getErrorHandler, getFilter, getFirstFilter, getLayout, getName, getThreshold, isAsSevereAsThreshold, setErrorHandler, setLayout, setName, setThreshold

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_PORT

public static final int DEFAULT_PORT

The default port number of remote logging server (4560).

Since:

1.2.15

See Also:

Constant Field Values

ZONE

public static final String ZONE

The MulticastDNS zone advertised by a SocketAppender

See Also:

Constant Field Values

Constructor Detail

SocketAppender

public SocketAppender()

SocketAppender

public SocketAppender(InetAddress address,
              int port)

Connects to remote server at address and port.

SocketAppender

public SocketAppender(String host,
              int port)

Connects to remote server at host and port.

Method Detail

activateOptions

public void activateOptions()

Connect to the specified RemoteHost and Port.

Specified by:

activateOptions in interface OptionHandler

Overrides:

activateOptions in class AppenderSkeleton

close

public void close()

Close this appender.

This will mark the appender as closed and call then cleanUp() method.

cleanUp

public void cleanUp()

Drop the connection to the remote host and release the underlying connector thread if it has been created

append

public void append(LoggingEvent event)

Description copied from class: AppenderSkeleton

Subclasses of AppenderSkeleton should implement this method to perform actual logging. See also AppenderSkeleton.doAppend method.

Specified by:

append in class AppenderSkeleton

setAdvertiseViaMulticastDNS

public void setAdvertiseViaMulticastDNS(boolean advertiseViaMulticastDNS)

isAdvertiseViaMulticastDNS

public boolean isAdvertiseViaMulticastDNS()

requiresLayout

public boolean requiresLayout()

The SocketAppender does not use a layout. Hence, this method returns false.

setRemoteHost

public void setRemoteHost(String host)

The RemoteHost option takes a string value which should be the host name of the server where a SocketNode is running.

getRemoteHost

public String getRemoteHost()

Returns value of the RemoteHost option.

setPort

public void setPort(int port)

The Port option takes a positive integer representing the port where the server is waiting for connections.

getPort

public int getPort()

Returns value of the Port option.

setLocationInfo

public void setLocationInfo(boolean locationInfo)

The LocationInfo option takes a boolean value. If true, the information sent to the remote host will include location information. By default no location information is sent to the server.

getLocationInfo

public boolean getLocationInfo()

Returns value of the LocationInfo option.

setApplication

public void setApplication(String lapp)

The App option takes a string value which should be the name of the application getting logged. If property was already set (via system property), don't set here.

Since:

1.2.15

getApplication

public String getApplication()

Returns value of the Application option.

Since:

1.2.15

setReconnectionDelay

public void setReconnectionDelay(int delay)

The ReconnectionDelay option takes a positive integer representing the number of milliseconds to wait between each failed connection attempt to the server. The default value of this option is 30000 which corresponds to 30 seconds.

Setting this option to zero turns off reconnection capability.

getReconnectionDelay

public int getReconnectionDelay()

Returns value of the ReconnectionDelay option.